Excellent processing properties and mechanical properties of polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) alloy resins are attributed to high heat resistance and impact strength of the polycarbonate resins and good processability and chemical resistance of the ABS copolymer resins. PC/ABS alloy resins exhibit better physical properties than ABS and can be produced at lower costs than PC.
Due to these advantages, PC/ABS alloy resins can be utilized in various applications. For example, PC/ABS alloy resins are widely used in not only electrical/electronic products, such as monitor housings, hard disks, printers and notebook batteries, but also in automobile parts, such as door handles, bumpers and instrument panels. Thus, high flame retardancy is required to make PC/ABS alloy resins suitable for use in molded articles, such as housings of electronic products.
A general method for imparting flame retardancy to a thermoplastic resin includes mixing the thermoplastic resin with a brominated or chlorinated compound as a halogenated flame retardant. Halogenated flame retardants exert sufficient flame retardancy in the case of fire but can cause mold corrosion and environmental pollution problems during processing. Particularly, halogenated dioxin generated from halogenated flame retardants upon fire or incineration is fatal to humans and is a major cause of environmental pollution. For these reasons, the use of halogenated flame retardants is legally restricted under the control of the Swedish Confederation of Professional Employees (TCO) in Europe.
Under such circumstances, technologies associated with the use of phosphorus-based flame retardants instead of halogenated flame retardants have been developed recently. Triphenyl phosphate (TPP) and bisphenol A bis(diphenyl phosphate) (BDP) are mainly used as phosphorus-based flame retardants. TPP can be added at a level of 10% by weight per the total weight of a resin to achieve a flame retardancy rating level of V-0. However, TPP undergoes bridging or evaporation during extrusion due to the low melting point thereof. BDP may cause a problem in the flowability of resins due to the high viscosity and high molecular weight thereof.